Spirit of the Son proves deity; one ascending–descending Lord

As God he became under law so that he might also become brother to those under law; for thus we have received the adoption. So if he had not become under law and from a woman, we would not even be brothers to the Lord and God by nature; but since he became so, we have been enriched with what is his. The inspired Paul makes proof of the matter, bringing at once: “And because you are sons, God sent out the Spirit of his Son into your hearts, crying: Abba, Father.” How then is the Spirit of the one from a woman and under law the Holy Spirit, through whom we also cry Abba, Father, unless Christ is God, being one and Son?

From Ephesians. “One Lord, one faith, one baptism, one God and Father of all, who is over all and through all and in all. But to each one of us was given the grace according to the measure of the gift of Christ; therefore it says: Having gone up into height he led captivity captive and gave gifts to humans. Now the ‘He went up’—what is it except that he also went down into the lower parts of the earth? The one who went down is himself also the one who went up above all the heavens, so that he might fill all things.” See again how great a word in this shows most clearly and vividly that Christ and Lord is one by an economic union of the Word brought together toward the human; for from both there is one true Son. For how is there one Lord? How one faith? Or how is baptism one? If there were two sons, there would altogether be two lords, a double faith, and baptism would not be one. For into whom have we believed? Or into whose name have we been baptized? But there is one Lord, one faith, one baptism. So it is clear that there is also one Son, even if the Only-begotten is understood as having become as we are. And who at all is the one who went up into height? Or who the one who came down into the lower parts of the earth? Therefore he himself went down humanly—for he let himself down into emptying and humbled himself, becoming obedient unto death—and went up with the flesh above all the heavens, so that he might fill all things.